This invention relates to disk data storage systems and more particularly to apparatus for reducing contamination and vibration of the disk data storage medium used in an optical disk data storage device. Even more particularly, this invention relates to placing a shroud over the disk data storage medium to reduce contamination and to reduce air turbulence and therefore reduce vibration caused by such turbulence.
Optical disk data storage devices employ a laser light source to write and read data on the surface of an optical disk storage medium. When writing at high densities, the laser must be very finely focused on the disk surface. This focusing requires a movable focusing element, such as a lens, near the surface of the disk, and the distance between the focusing element and the surface of the disk must remain constant. The focusing element is contained in a read/write head and is movable so that it can refocus the laser beam if this distance changes. However, a very rapid change in the distance between the focusing element and the disk surface, such as that caused by vibration of the disk surface, cannot be corrected to keep the laser beam finely focused. Therefore, vibration of the disk results in a wider focus point and therefore a wider track made by the beam as the disk rotates underneath it. Reducing disk vibration results in a more narrow focus point, and a narrower track width; therefore, more tracks can be stored on the surface of the disk storage medium.
One cause of vibration of the disk is air turbulence over the surface as the disk rotates. Any rotating disk acts as a natural pump to move air from the inner diameter of the disk to the outer diameter. If the disk surface is exposed to ambient air, air currents caused by any obstruction near the disk, such as the read/write head, will cause turbulence of the air near the surface and such turbulence causes the disk to vibrate. Vibration results in a wider focus point and places a drag on the rotation of the disk. Reducing the turbulence reduces vibration of the disk thus decreasing track width to allow more data storage on a disk, and thus decreasing drag to lower the energy required for rotation of the disk.
Another problem in disk data storage devices is contamination by small particles of dirt or other foreign material on the surface of the disk. Since an optical read/write head in an optical disk storage device is located farther from the disk surface than a magnetic read/write head in a magnetic disk storage device, optical devices are less sensitive to contamination, however, care must still be taken to reduce such contamination. One way to reduce this contamination is to provide a positive air pressure over the disk surface using filtered, uncontaminated air. However, this positive air pressure implies a larger flow rate which increases the chance for turbulent flow across the disk.
It is thus apparent that there is a need in the art for a device to reduce the turbulent caused vibration of a disk storage medium as it rotates underneath a read/write head. There is also a need to provide a positive air pressure over the disk storage medium using filtered air to prevent contamination as would be caused by ambient, unfiltered air near the surface of the disk. The air shroud disclosed herein is directed to satisfying these and other needs.